Telephone mouthpiece voice silencer with plural silencing chambers



Aug. 9, 1949.

Filed June 17, 1946 L. TELEPHONE MOUTH S. SCHER PIECE VOICE SILENCERWITH PLURAL SILENGING CHAMBERS 2 Sheets-Sheet 1 INVENTOR. L OU/S 5.SCHEE.

ATTORNEY.

Aug 9, 1949. L. s. SCHER 2,473,733

TELEPHONE MOUTHPIECE VOICE SILENCER WITH PLUR'AL SILENCING CHAMBERSFiled June 1'7, 1946 2 Sheets-Sheet 2 INVENTOR. LOU/5 5. SCHER.

M A TT'ORNE Y Patented Aug. 9, 1949 umrso PATENT OFFICE TELEPHGNEMOUTHPIECE VOICE SILENCER WITHPLUR'AL'SILENCING CHAMBERS Louis. S.Scher, New York, N. Y. Application June17, 1946, Serial N'0."677,389

fiClaims. (Cl. 181-434) The present invention relates to"an'atta'chmerit for telephones'by meanscf which the voiceof thespeaker'can be "substantially completely mines 'to ensure privacy in thepresence of others.

Voice silencers fortelephones are-wel-l known. These essentiallycomprise a chamber lined or provided with sound-deadening"material suchas felt, to provide acoustic absorption. While these devices arereasonably satisfactory and give a substantial amount 'ofprivacy totelephone conversations, they do have recognized disadvantages whichhave not, so far, been overcome. One such disadvantage residesin thefact'thatthe voice ofthespeakeris unclear to the listener at theotherend of the line. 'This'is partly due to interference caused byout-of-phase reverberation or fixed low-pitchedresonance-and partly theresult of the buildin up of back-pressure where incorrect ventingor lack'ofventing-exists. Although such back-pressureis slight it has anextr'emelyadverse efiectprobabl'y due to air pressure on thetransmitterdiaphragm, besides low pitched resonance increasing undesirable tonalqualities. Whatever the precise cause or explanation, priorvoicemu-filersfor telephones have not been entirely satisfactory eitherfrom'anacousticalor from a mechanical or constructional point of view.

It is, consequently, anobject of this invention to-overcome thedeficiencies-of prior telephone voice mufilersand to provide anew andimproved device which is correctly designed acoustically and which ismechanically and structurallyperfected, as for instance, shaping themufiler to conform. to the. telephone stand as well asrthe mouth of theuser, without-any mechanical interference; the voice mufiler beingsoshaped, it will not interfere with normal lifting and hang in up ofthe telephone handset.

'Anotherobject of the invention is to provide a telephone voicemutter-Which ensures privacy without need of reducing the volumeexcessively for the listener at the other end oi the line, and Withoutappreciable loss of fidelitycf tone.

A further object of the invention is to construct a telephone voicemuffler in which backpressure or sound distortion cannot be built upduring even forcefulnseand in which correct and adequate ventingisprovided for et the same time 'setting the natural pitch of the voicemuffler considerably higher than would 'bethe case without venting.

'A still further object or the invention resides, in the useoi arelatively large massoi'sound-abexcessivesound absorption-and withoutadverse effectpn'the venting of the rnnfller as a whole.

Other objectsandadvantages lie in the various structuralcombinations anddetails hereinaftendeseribed.

In the accompanying drawings:

Fig. 1 illustrates my new telephone voice muffler as applied to amoderntelephone.

Fig. 2 is an el-evational View of the mufiler per-'se.

-Fig. 3--i-s aplan view of Fig. 2.

Fig.4 is-a bottom view of Fig. 2.

Fig. 5 is a view-looking from right to left of Fig. 2.

Fig. '6 is a view-looking from left to right of Fig. 2.

Fig. 7 is an enlarged sectional view of my new mu'fller showing inbrokenlines a portion of the associated telephone.

Fig. 8 is a detail view of the exhaust box used in the form of mufflershown in Fig. 7.

Fig. 9. is aviewsimilar to Fig. 7, of asomewhat modified construction ofmufiler.

new voice mufller. is essentially comprised of atelephonetransmitterengaging portion ill. and a. mouthpiece portion ll, each of which iscomposed of a. suitable plastic material of rigi non-deformable nature.Bakelite, acetate and other .materials. of similar types or rigid waxedpaperioricastlightweight metal. are eminently satisfactory forthisipurpose.

. Portion. H1 is. of generally annular form-and is provided withaplurality .of equispaced springs [2,usua1lythreein number, which engageand hold the. muffler. in'place on the. telephone transmittenT, the:outer edge of which is received within the annulus of portion 10, asbest shown in '7 of the drawings. Portion lo has'an. upstanding portionl3.of the inverted U-shaped crossesection whichextends. partially aroundthe annulus ;of 2 portion Ill, somewhatv more. than ,a semi-circle. .rIn.plan, portion I3 is crescentshaped,.as. will be best appreciated fromFig. 3. Due to. theconstruction, just recited, it will be apparent thata crescent-shaped chamber-is formed within portion l3 and this chamberis substantially filled with sound-absofhg sound dea'dening material I4which is not the conventionally employed felt. I have found thatartificial or synthetic sponge constitutes aunique and highlyefilcaciousmaterial and that it is light and resilient, propertiesrendering it highly suitable 'for thenipresent .purpose. .:It is,moreover, characterized by numerous :small passages forming a veritablenetwork into which sound waves can penetrate and be absorbed. Thismaterial can be removed and rinsed in water or sterilized and used overagain when dried. It does not have the massiveness or weight of feltand, therefore, results in more satisfactory sound absorption whichrenders the voice more intelligible to the listener at the other end ofthe line. It does, however, efiectively mufile the voice of the speakerto those within normal hearing range. An arouate perforated shield it,preierably fabricated from a light metal such as aluminum, is disposedbetween the inner surface or material I4 and the inner Wall of portionI3,

It will be noted that material Hi does not completely fill thecrescent-shaped chamber formed by th combined transmitter-engagingportion and mouthpiece portion and that the lower edge of shield I5extends below the material It. This arrangement forms a chamber ZIwithin mouthpiece portion I I. This chamber is in communication with themouthpiece via the perforations in shield I5. The chamber is maintainedagainst diminution in size or change of shape by means of an exhaust boxlI forming a chamber I6 which is held in place by a suitable fasteninginstrumentality, such as the screw I8, th threaded end of which engagesa nut I9 countersunk in the plastic body of the mouthpiece portion II,as shown.

It will be further noted that mouthpiece portion II is provided with aplurality of openings 20. These openings are located at critical pointsand constitute an important feature of the present invention; they notonly provide an evenly distributed escapement for back pressure, butalso raise the natural resonance pitch of the voice muffler as in anopen flutepipe versus a closed pipe, a well-known fact in the science ofsound. since exhaust box H is also provided with strategically locatedapertures, it will be understood that back-pressure escapement will passthrough chamber It Without appreciable escapement of sound. All otherescapement openings form long restricted passages in the thick sectionsof mouthpiece portion II, also create resistance to escapement of soundfrom the Voice mufiler.

In Fig. 9, the structure is substantially the same as that alreadydescribed except that in some instances it has been found desirable toplace the exhaust box IIa on the exterior of mouthpiece portion IIa,rather than in the interior as in Fig. 7. In this way, the chamber I6ais exterior and communicates with the reduced chamber 2Ia, withinportion Ila. Back-pressure is avoided since through communication isprovided via apertures Ila, openingsflfla, andthe perforated guard I5a.

The foregoing is presented as illustrative and not as limitative asother modifications may be resorted to without departing from the spiritor principles hereof. In particular, soft fabric inserts may be employedinstead of springs I2 and Ila or any other suitable means may beprovided for engaging and holding a telephone transmitter of any of theusual designs. The two main portions of the present mufller are readilyassembled and disassembled and all members can be convenientlysterilized without damage thereto. 7

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. A voice muffler comprising a telephon transmitter-engaging portionand a mouthpiece portion readily attachable to and detachable from eachother, sound absorbing material of nonnbrous nature within saidtransmitter-engaging portion and means for preventing back-pressure insaid mufiier during use, said telephone transmitter-engaging portionbeing of generally annular form and having an upstanding invertedU-shaped portion of crescent shape, the said sound-absorbing materialbeing disposed within and completely filling the said upstanding portionand extending therebeyond into said mouthpiece portion, and a hollowexhaust box having openings communicating with the interior of saidmouthpiece portion.

2. A voice mufller comprising a telephone transnutter-engaging portionand a mouthpiece portion readily attachable to and detachable from eachother, sound absorbing material iOf nonfibrous nature within saidtransmitter-engaging portion and means for preventing back-pressure insaid muflier during use, said telephone transnutter-engaging portionbeing of generally annular form and having an upstanding invertedU-shaped portion of crescent shape, the said sound-absorbing materialbeing disposed within and completely filling the said upstanding portionand extending therebeyond into said mouthpiece portion, a hollow exhaustbox having openings communicating with the interior of said mouthpieceportion, and a perforated shield along one side of said sound-absorbingmaterial in the transmitter-engaging portion and extending into saidmouthpiece portion.

3. A voice mufiler comprising a telephone transmitter-engaging portionand a mouthpiece portion readily attachable to and detachable from eachother, sound absorbing material of non fibrous nature within andcompletely filling said transmitter-engaging portion and means forpreventing back-pressure in said mufiler during use, said back-pressurepreventing means including a series of openings through the mufiler wallcommunicating th interior of the muffler with the outer atmosphere,certain of which openings being laterally located to improve tonalqualities, and a hollow exhaust'box communicating with the mufiler tointroduce a tortuous path for the relief of air pressure withoutimpairing theefficiency of the sound-retaining qualities.

4. A voice mufiler comprising a telephone transmitter-engaging portionand a mouthpiece, portion, sound absorbing material within saidtransmitter-engaging portion and means for preventing back-pressure insaid mufller during use, said telephonetransmitter-engaging portionbeing of generally. annular form and having an upstanding invertedU-shaped portion of crescent shape, the said sound-absorbing materialbeing disposed within and completely filling the said upstanding portionand extending therebeyond into said mouthpiece portion, a hollow exhaustbox on the wall of the mouthpiece portion, and having openingscommunicating the interior of said exhaust box with the interior of themouthpiece portion and having other openings communicating the interiorof the exhaust box with the outer atmosphere.

5. A voice mufller comprising a telephone transmitter-portion and amouthpiece portion, sound absorbing material of non-fibrous naturewithin said transmitter portion and means for preventing back-pressurein said mufller during use, said back-pressure preventing meansincluding a series of openings through the mufiler wall communicatingthe interior of the mufller with the outer atmosphere, certain of whichopenings being laterally located to improve tonal qualities, and ahollow exhaust box communicating with the muiller to introduce atortuous path for the relief of air pressure without impairing theefflciency of the sound-retaining qualities.

6. In a voice muflier having a telephone transmitter engaging portion,which is of generally annular form and has a hollow upstanding invertedU-shaped part of crescent shape, and a mouthpiece portion readilyattachable to and detachable from said transmitter-engaging portion;sound-absorbing material of non-fibrous nature within and completelyfilling said upstanding part and extending therebeyond into saidmouthpiece portion, th mouthpiece portion having walls of non-uniformthickness, means for preventing back-pressure in said muiiler duringuse, said means including a series of openings through the thickenedpart of the walls of said mouthpiece portion forming narrow restrictedpassages communicating the interior or the muffler with the outeratmosphere, and being laterally located to improve tonal qualities, anda hollow exhaust box having openings communicating with the mouthpieceportion, and having other openings communicating the exhaust box withthe outer atmosphere to introduce a tortuous path, all for relieving ofair pressure without impairing the efiiciency of the sound-retainingqualities.

LOUIS S. SCHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 730,101 Dunihue June 2, 19031,041,545 Williamson Oct. 15, 1912 1,419,606 Benedict June 13, 19221,425,958 Gelb Aug. 15, 1922 2,225,509 Schober Dec. 17, 1940 2,245,724Scher June 17, 1941 FOREIGN PATENTS Number Country Date 26,315 GreatBritain 1908 537,196 Germany Oct. 30, 1931

